Patent leather



May 24, 1960 H. S. LYNESS PATENT LEATHER Filed May 22, 1958 DYED BLACK SKIN AND APPLY LINSEED OIL DRY STARTING MATERIAL AND DRY

APPLY NYLON LACQUER As A SPRAY AND DRY APPLY FINISH COAT OF LINSEED OIL DRY AT' FINISHED PATENT LEATHER IN VEN TOR.

United States Patent O PATENT LEATHER Horatio Seymour Lyness, 17 Carey St., Nahant, Mass. Filed May 22, 1958, Ser. No. 736,995

4 Claims. (Cl. 117-76) This invention relates to leather finishing, in particular to that type commonly known as patent leather, and provides a patent leather finish of increased durability and resistance to the damaging effects of cold weather.

Patent leather is characterized by an extremely glossy finish but its usefulness has been seriously impaired by the tendency of the finish to crack or check during use, particularly in cold weather. Although numerous methods have been proposed for reducing or eliminating this checking none has heretofore proved entirely satisfactory.

The manufacture of patent leather consists generally of the application of several coatings of linseed oil or similar oil or varnish material, each of which is dried at approximately 150 F. before the next coating is applied. A smooth lustrous japanned surface is thus gradually built up. In addition to linseed oil, soy bean oil and other varnish finishing oils, as well as oil incom- 'bination with alkyd resins, are commonly used to form a japanned finish. One common technique is to apply first a daub coat of thick linseed oil to prime the leather, then when this is partially dried to apply the blue coat, a light coat of linseed and/ or soy bean oil to which color has been added, for the purpose of making the color uniform. When that has been dried the finish coat is applied, a coat of linseed and/or soy bean oil, and the coating is caused to harden through the action of sunlight or infra-red radiation.

Patent leather finishes formed in this manner tend to become checked or crazed through wear, especially in cold weather. The uniform high gloss is then largely lost. Commonly a patent leather finish will have been deteriorated by checking or crazing in as few as five or six wearings in the winter.

The present invention largely overcomes this effect and provides an improved patent leather finish having uniform gloss which is in all respects equal to or superior to those heretofore made but which in addition is of such increased flexibility and elasticity as to resist checking or crazing. The finish of this invention moreover is of increased stability and do not become brittle with age as does conventional patent leather finishes. Leather produced by this invention accordingly has a much longer shelf life.

The patent leather finish of this invention is built up in the same manner as in conventional processes, that is by the repeated application of coatings of a japanning composition such as linseed oil or other oil or varnish composition. The invention however includes the additional step of applying to the leather an additional coat of a nylon lacquer at some stage before the final patent leather finish coat is applied. Preferably the coat of nylon lacquer is sprayed onto the partly finished leather over two coats of oil or varnish, and after drying, the final finish coat is applied. Other entirely satisfactory techniques, however, consist in mixing the nylon lacquer with the oil or varnish applied in one of the early base coats, before the application of the final finish coat.

Additional improvements to the finish produced by this invention may be had by adding a plasticizer to the nylon 2,937,957 Patented May 24, 1960 lacquer to produce a finishof increased softness. Any of numerous known plasticizers for nylon may be used, and the amount in any case will depend on the desired effect. Finishes of increased toughness and heat resistance may also be formed by incorporating a polymerization catalyst, e.g. a dryer, to enhance the degree of polymerization and cross linking of the oil finish. Catalysts may also be included to cause additional polymerization and cross linking of the nylon.

Nylon lacquers suitable for use in this invention include in general any solution of nylon in an inert solvent, containing from about 5 to about 20 parts of nylon by weight. Suitable solvents for the lacquer include alcohol and mixtures of a solvent with a non-solvent, for instance a mixture of alcohol and water.

The nylon component of the lacquer may be any of the well known alcohol-soluble nylons many of which are commercially available. The term nylon .is used herein to designate high molecular weight condensation polymers and interpolymers which contain amide linkages formed by the reaction of a carbonyl (or carbonyl derivative) group with an amide group having a hydrogen atom joined to the nitrogen atom, and which are capable of being formed into films, foils or fibers. Materials of this type are described in U.S. Patents Nos. 2,252,555 and 2,252,557 and are also commercially available as Zytel 63 and 69 (sold by Du Font) and as BCI No. 819 (sold by Belding Corticelli Industries). Of these, those capable of being cross linked to an insoluble infusible polymer are preferred, e.g. BCI No. 819.

The invention is described in detail below with reference to a preferred procedure selected for purposes of illustration and graphically outlined in the accompanying ilow sheet of the drawings. In these procedures the steps other than the application of a nylon lacquer-containing coating are conventional steps in the manufacture of patent leather and are described as representative thereof.

Example 1 A top grain chrome tanned calf skin dyed to a uniform jet black is first coated with the. daub coat of thick boiled linseed oil which is then partly dried to a tacky surface at 150 F. A second coating of the blue coat of a thin mixture of linseed oil and soy bean oil pigmented to a black color, is then applied and again dried to a tacky finish at 150 F. The nylon lacquer is then sprayed on. This consists of a solution of:

7 parts by weight of ethanol 3 parts by weight of water 2 parts of BCI No. 819, believed to be an alkoxy substituted nylon of hexamethylene diamine and adipic acid.

The mixture is heated with stirring to F., is then permitted to set overnight to gel, and is then reheated to 100 F. preliminary to being sprayed on the leather.

After its application, the nylon lacquer coat is permitted to dry, and the final finish coat of linseed oil and soy bean oil is applied. The leather is then dried at F., in the presence of infra-red radiation, until thoroughly hard.

The finished leather is of the same uniform black glossiness characteristic of the finest patent leather but is of such increased flexibility and durability that even when incorporated in shoes there is a complete freedom of checking for several months, even when worn in cold weather. This resistance to checking is moreover retained by the finish even after periods of storage of as long as a year; there is little or none of the brittleness which comes to conventional patent leather finishes upon aging.

3 Example 2 An extremely durable patent leather finish may be formed by adding cross linking agents to the nylon lacquer to form an insoluble infnsible nylon film. A suitable practice is to add-the agents to the lacquer just prior to its application to the leather. As an example, the same procedure as set forth in Example 1 may be followed withthe exception that there is added to the lacquer first 78% (based on the weight of nylon) of tributylamine and then -6% (based on the weight of nylon) of maleic anhydride. After the lacquer has been applied and dried, the nylon containing coating is cured at 200 F. for about 8-10 minutes. The final oil or varnish coating is then applied and the leather is finally processed in the usual manner.

Although this invention has been described with reference to its preferred embodiments, it is contemplated that obvious modifications will occur to those skilled in the art and that such may be made without departing from the scope of the invention. In particular the advantages of the process may be realized with any of the numerous techniques of forming patent leather finishes and the various compositions may be modified to suit the requirements of the various manufacturers.

Having thus disclosed my invention and described in detail preferred embodiments thereof I claim and desire to secure by Letters Patent:

1. The method of finishing leather comprising applying a coating of a liquid japanning composition to a dyed black skin, then applying a coating comprising a solution of a polyamide of the nylon type in an inert solvent and causing it to dry, then applying a further coating of a japanning composition, and causing said coatings to dry to a glossy iapanned finish.

2. The method defined by claim 1 wherein the nylon solution comprises a polyamide of the nylon type dissolved in a solvent liquid comprising alcohol.

3. The method defined by claim 1 wherein the solution of a polyamide of the nylon type is mixed with a liquid japanning composition.

4. The method of producing patent leather comprising the steps of applying a coating of boiled linseed oil to a dyed-black skin, drying the oil upon the skin to a tacky consistency, applying a black mixture of linseed and soy bean oil as a second coat and again drying to a tacky consistency, then spraying upon the coated skin a hot lacquer of a polyamide of the nylon type dissolved in ethanol, drying the lacquer, and applying a final finish coat of linseed oil and soy bean oil.

References Cited in the file of this patent UNITED STATES PATENTS 2,071,250 Carothcrs Feb, 16, 1937 2,083,040 Shuey June 8,1937 2,204,520 Walker et al June 11, 1940 2,265,127 Bolton Dec. 9, 1941 2,302,332 Leekley Nov. 17, 1942 2,342,387 Catlin Feb. 22, 1944 2,387,395 Hedges et al Oct. 23, 1945 2,443,450 Graham et al. June 15, 1948 

1. THE METHOD OF FINISHING LEATHER COMPRISING APPLYING A COATING OF A LIQUID HAPANNING COMPOSITION TO A DYED BLACK SKIN, THEN APPLYING A COATING COMPRISING A SOLUTION OF A POLYAMIDE OF THE NYLON TYPE IN AN INERT SOLVENT AND CAUSING IT TO DRY, THEN APPLYING A FURTHER COATING OF A JAPANNING COMPOSITION, AND CAUSING SAID COATINGS TO DRY TO A GLOSSY JAPANNED FINISH. 